In many doors, windows and other such elements provided with a rotatable handle, it is desirable that a part that can be turned or rotated by means of the handle can be selectively coupled to or disengaged from another part. The other part can either be a similarly rotatable part or a stationary part.
When both parts are rotatable, it may be desirable in a disengaged position, for example, to allow the handle to be turned without affecting the other part and, in a coupled position, to allow a rotation movement of the handle to be transferred to the other part. The other part can then be, for example, a swivel pin, such as a handle shank or lever handle shank, which is in turn able to transfer the rotation movement to a follower, a bolt, an espagnolette, a lock or some other device for influencing the state of the door or of the window. In the coupled position, normal operation therefore occurs by way of the handle. In the disengaged position, by contrast, the state of the door or of the window remains unaffected if the handle is turned.
Disengagement of the handle from another rotatable part is sometimes referred to as “free swing”. This kind of selective disengagement can be used, for example, as a child safety measure, in order to prevent an external door or a window from being opened from the inside, or in order to prevent damage to a lock or the like coupled to the handle if excessive forces are applied to the handle when the lock is in the locked position.
When the other part is a stationary, non-rotatable part, the rotatable handle can be conventionally fixed or continuously coupled by means of a handle shank or lever handle shank to a bolt, an espagnolette, or a lock, for example, or some other device for influencing the state of the door or the window. Disengagement and coupling between the rotatable handle and the stationary part can then be used, in the disengaged position, to allow operation and, in the coupled position, to block the handle and thereby prevent operation of the door or the window. The coupling between the handle and the stationary part can in this respect be said itself to constitute a lock. This kind of selective disengagement and coupling between the rotatable handle and the stationary part can be used as a child safety measure, for example, or in order to prevent unauthorized persons from operating a door or a window.
In both cases the disengagement and coupling between the rotatable handle and the other part can be achieved manually, for example by operating a mechanical button, a lock cylinder or the like. Recently, however, it has become increasingly more common to bring about this disengagement and coupling by electro mechanical means. This allows disengagement and/or coupling, for example, only when an authorized user has first entered a code via a keypad or has provided an identification via a card reader for electronic cards.